JPH1158192A - Super-abrasive grinding wheel for high speed grinding and high speed grinding work method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To carry out contouring grinding having a high finishing accuracy with a good efficiency. SOLUTION: A workpiece W and super-abrasive grains grinding wheel P are relatively moved in a workpiece rotating axial direction while rotating both components respectively, and a surface of the workpiece W is grindingly- worked along its rotating axial direction by 1 pass. Its grinding circumferential speed is set to 120 m/sec or more, the inclining angle θ of a taper part 1b is set to 10 to 45 degrees, more preferably, it is set to before and after 15 degrees. The average particle diameter of the super-abrasives is set to 100 to 500 μm, a concentrating degree is set to 150 or more, resistance force of vitrified bond is set to 7.0 kgf/mm<2> or more, and a high temperature hardness at 300 deg.C is set to 450 Hv or more. When the inclining angle and the average particle diameter are set, a finishing accuracy satisfied in a circularity and surface roughness is obtained in circumferential speed of 120 m/sec by one pass.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superabrasive grain grinding wheel for high-speed grinding and a high-speed grinding method capable of performing high-precision and high-efficiency grinding in one pass while rotating a workpiece. TECHNICAL FIELD The present invention relates to a superabrasive grain grinding wheel for high-speed grinding and a high-speed grinding method for grinding a material having a notch, a groove, or a concave portion with high accuracy and high efficiency.

[0002]

2. Description of the Related Art In today's grinding method, a workpiece and a super-abrasive grindstone are relatively moved in the direction of a rotation axis of a workpiece while rotating each, and the surface of the workpiece is moved in one pass along the direction of the rotation axis. Some of them are ground. This processing is generally called contouring grinding.

[0003] The superabrasive grindstone used in this processing method has a straight portion for finish grinding whose outer peripheral grinding surface is parallel to the workpiece rotation axis, and a straight portion connected to the straight portion and connected to the workpiece rotation axis. It consists of a taper part for rough grinding inclined to the other side (see Fig. 2). In contour grinding with this super-abrasive grindstone, rough grinding is first performed on the tapered part of the super-abrasive grindstone, and then finished with the straight part Perform grinding. Examples of this type of superabrasive grindstone include those described in JP-A-7-156047 (JP-A-1) and JP-A-8-99257 (JP-A-2).

[0004]

In recent years, in order to improve the grinding efficiency, super-abrasive grindstones are machined at a peripheral speed of 80 m / sec or more.
There is a description that the peripheral speed is increased to 0 m / sec. Further, a grinding device having a peripheral speed of 200 m / sec is also commercially available. On the other hand, since it is necessary to improve the accuracy of various machines, higher finishing accuracy, such as surface roughness and roundness, of components of the machine is required.

However, in the conventional contouring grinding, 1
With the idea that sufficient surface roughness and roundness cannot be obtained with the pass, and that if the peripheral speed is increased, their finishing accuracy will be reduced, reduce the depth of cut to obtain the required accuracy. The work is processed by passing the work several times, which is not very efficient. In particular, when there is a notch, a groove, or a recess in a part of a workpiece, the presence of the notch or the like becomes a greater problem in obtaining high accuracy.

[0006] Under the circumstances described above, the present invention provides a peripheral speed of 120
It is an object to perform contouring grinding with high finishing accuracy even in ultra-high-speed grinding at m / sec or more.

[0007]

In order to solve the above-mentioned problems, the present invention first sets the peripheral speed to 120 m / sec or more, and then sets the inclination angle θ of the tapered portion with respect to the workpiece rotation axis at 10 to 45. It was a degree.

[0008] As described in the above publication 2, the prior art generally has a peripheral speed of 120 m / sec or less, and the inclination angle of the tapered portion is 10 m.
Degrees or less. The reason why the inclination angle is set to 10 degrees or less is that, when the inclination angle is increased, the grinding resistance is increased, the calorific value is increased, and grinding burns and hardness decrease are caused.

However, if the traverse speed is constant and the peripheral speed increases, the total area of the grinding surfaces participating in grinding also increases, thereby reducing the amount of grinding in one revolution of the superabrasive grinding wheel.

On the other hand, is considered a tapered portion to bear almost all of the grinding resistance, the normal grinding force F _n is, when all the grinding resistance tapered portion to bear a F, since the F cos theta, the inclination angle theta is If it increases, it will decrease (Fig. 6
reference).

Therefore, it is not considered that the finishing accuracy such as the surface roughness and the roundness simply decreases even if the peripheral speed is high and the inclination angle θ is large. Based on this idea, the following example was performed, and the above-described inclination angle was obtained.

Further, the grain size of the super-abrasive grains affects the machining efficiency. In the present invention, since the rough grinding is performed to the finish grinding in one pass, the machining efficiency needs to be high, and the grain size is less than 100 μm. However, it is too fine and is not suitable for rough grinding in one pass, and if it exceeds 500 μm, a problem occurs in terms of finishing accuracy in one pass. For this reason, in consideration of the processing efficiency of the one-pass grinding, the particle size of the superabrasive grains is 100 to 5
It is set appropriately between 00 μm.

[0013] Furthermore, the degree of concentration of superabrasive grains also affects the processing efficiency. However, if the degree of concentration is low, the grinding rate decreases.
For pass grinding, 150 or more is required. Incidentally, it is preferable that the degree of concentration is high, but the degree of concentration that has been put to practical use is 25.
It is up to about 0.

For grinding at a peripheral speed of 120 m / sec or more, the grindstone (abrasive layer) needs to have rigidity and high-temperature hardness. In practical use, a vitrified bond superabrasive grindstone has resistance to the vitrified bond. Bending power: 7kgf
/ Mm ² or more, high-temperature hardness at 300 ° C .: 450 Hv or more is desired.

[0015]

First, a workpiece W shown in FIG. 3 was ground as shown in FIG. 4 with a superabrasive grindstone P shown in FIG. 2 under the experimental apparatus and experimental conditions shown in FIG. In the figure, S is 2
mm. Also, a superabrasive grindstone P for contouring grinding
Is required to have high abrasive grain holding power, high bond strength and high high temperature strength, and CBN abrasive grains (average particle size: 200),
Concentration: 200% vitrified bond. Further, in the example, as shown by the physical property values in FIG.
%, A vitrified material whose high-temperature hardness at 300 ° C. was improved by 38% was used. The results are shown in FIGS.

The roundness and surface roughness were measured using a roundness measuring device and a surface roughness measuring device, and the grinding resistance was measured using a dynamometer 9167A type manufactured by Kistler. Regarding the wear amount of the super-abrasive grindstone, the wear shape is gray cast iron (FC20)
And the shape was measured with a surface roughness meter. Incidentally, with respect to the cut amount of one pass, it is preferable that the diameter is 0.2 mm or more in order to sufficiently obtain the effect of the present invention. If it is less than this, the significance of providing the tapered portion 1b is lost.

From FIGS. 7 to 10, when the inclination angle θ is increased, the surface roughness and the wear amount of the superabrasive grindstone decrease, and the normal
Both the tangential grinding resistances Fn and Ft decrease. It is considered that the decrease in the surface roughness is affected by the change in the length of the straight portion 1a due to the decrease in the wear amount of the superabrasive grindstone. Further, the reason why the grinding resistance was reduced is considered to be that the contact area between the tapered portion 1b and the workpiece W was reduced. Thus, it can be understood that the inclination angle θ of the tip of the superabrasive grindstone has a great effect on the contouring grinding performance.

Further, from FIG. 11, the value of the roundness decreases as the inclination angle θ increases. This is probably because the deflection of the workpiece W described later has been reduced by the reduction in the grinding resistance.

From the above considerations, it is most preferable that the inclination angle θ is about 15 °, and there is no difference in the surface roughness of the workpiece at the lower limit of 10 ° and the upper limit of 45 °.

As shown in FIG. 12, the roundness and the surface roughness of the embodiment are improved by about 30% as compared with the conventional example. Further, the wear length L of the superabrasive grindstone (see FIG. 5) is reduced by 40%. Therefore, it can be understood that the working example has not only abrasion resistance but also good working accuracy. In addition, it was found that in the portion of the groove a, a recess was formed in the workpiece cross-sectional profile, and the value of roundness was increased. It is considered that the cause of this dent is that the intermittent grinding phenomenon occurred in the groove portion, and the deflection of the workpiece was elastically recovered. FIG. 11 shows the roundness and the like of the workpiece after the processing of 29 × 10 ³ mm ³ .

[0021]

As is apparent from the above description, according to the present invention, the inclination angle of the tapered portion, which has been considered to be unfavorable in the past, is increased to 10 to 45 degrees in machining at a peripheral speed of 120 m / sec or more. By doing so, highly accurate contouring grinding can be performed with high efficiency.

Further, even if a notch, a groove, and a recess exist on the surface to be ground of the workpiece, the taper portion comes into contact with an end face of the notch or the like because the inclination angle of the taper portion is larger than in the past. In this case, the normal resistance at the contact point is reduced, and the accuracy deterioration such as roundness is also reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing an experimental apparatus and experimental conditions in one embodiment.

FIG. 2 is a schematic view of a main part of a high-speed grinding superabrasive grinding wheel.

3A and 3B show a workpiece, wherein FIG. 3A is a left side view, and FIG.

FIG. 4 is an explanatory view of a grinding action.

FIG. 5 is an explanatory diagram of superabrasive grinding wheel wear.

FIG. 6 is a graph showing a relationship between a superabrasive grinding wheel and a grinding resistance of a workpiece;
(A) is a side view, (b) is an enlarged view of a main part.

FIG. 7 is a diagram showing the relationship between the accumulated material removal amount and the workpiece surface roughness in the embodiment.

FIG. 8 is a diagram showing the relationship between the accumulated material removal amount and the wear length in the example.

FIG. 9 is a graph showing the relationship between the accumulated material removal amount and the normal grinding resistance in the embodiment.

FIG. 10 is a diagram showing the relationship between the accumulated material removal amount and the tangential grinding resistance in the example.

FIG. 11 is a table showing the relationship between the inclination angle of the tapered portion and the roundness in the embodiment.

FIG. 12 is a comparison table between an embodiment and a conventional example.

FIG. 13 is a comparison table of physical property values of a vitrified bond of an example and a conventional example.

[Explanation of symbols]

 P Super-abrasive grindstone W Workpiece θ Tapered part inclination angle 1a Straight part 1b Tapered part a Groove

Claims (4)

[Claims] 1. A grindstone for grinding a workpiece W and a superabrasive grindstone P in a single pass along the rotational axis direction by relatively moving the workpiece W and the superabrasive grindstone P in the direction of the rotational axis of the workpiece. A super-abrasive grindstone for high-speed grinding having a peripheral speed of 120 m / sec or more, wherein the super-abrasive grindstone outer peripheral grinding surface has a straight portion 1a for finish grinding parallel to the workpiece rotation axis, and the straight portion 1a. And a tapered portion 1b for rough grinding that is inclined with respect to the rotation axis of the workpiece.
The super-abrasive grindstone for high-speed grinding, wherein the inclination angle θ is 10 to 45 degrees. 2. The superabrasive having an average particle size of 100 to 500 μm.
m, concentration level is 150 or more and flexural strength is 7.0 kg
The superabrasive grinding wheel for high-speed grinding according to claim 1, wherein the superabrasive wheel for high-speed grinding is made of a vitrified bond having a f / mm ² or more and a high-temperature hardness at 300 ° C of 450 Hv or more. 3. A super-abrasive grinding wheel for high-speed grinding according to claim 1 or 2, wherein the peripheral speed of the grinding wheel is 120 m / sec or more.
A high-speed grinding method characterized by grinding in one pass while rotating a workpiece W. 4. The high-speed grinding method according to claim 3, wherein at least one of a notch, a groove, and a recess exists on the surface to be ground of the workpiece W.